The diploid nucleus of a plant cell holds 2.0 × 10¹⁰ bp of DNA…

(a) Length. $2.0 \times 10^{10}\ \text{bp} \times 0.34 \times 10^{-9}\ \text{m} = 6.8\ \text{m}$. This is far longer than a nucleus, which is only a few micrometres across. So the DNA must be packaged.

(b) Nucleosomes. $\dfrac{2.0 \times 10^{10}\ \text{bp}}{200\ \text{bp}} = 1.0 \times 10^{8}$ nucleosomes, the "beads" of the beads-on-string chromatin.

(c) Histones. Each nucleosome core is a histone octamer, $8$ molecules: $8 \times 1.0 \times 10^{8} = 8.0 \times 10^{8}$ histone molecules.

(d) Turns. $\dfrac{2.0 \times 10^{10}\ \text{bp}}{10\ \text{bp}} = 2.0 \times 10^{9}$ turns.

(e) The bacterium. $\dfrac{1.02 \times 10^{-3}\ \text{m}}{0.34 \times 10^{-9}\ \text{m}} = 3.0 \times 10^{6}\ \text{bp}$. In a bacterium this DNA is held with positively charged proteins in a region called the nucleoid.